岩土工程技术

Development and Experimental Comparative Analysis of the Stress Effect Direct Shear Apparatus for Small Load Rock Joint

Li Chao, Cao Xiaofeng, Yan Jun

2018, 32(6): 271-276,323. doi: 10.3969/j.issn.1007-2993.2018.06.001

[Abstract](46) [PDF 8875KB](10)

Abstract:
Due to large hydraulic loading force and the difficulty of keep normal stress constant,there are many defects in conventional direct shear apparatus,such as the inadequacy of small load rock joint and low accuracy of shear strength results.Based on consistency of principle of instrument and reliability of test result,a stress effect direct shear apparatus of small load rock joint has been developed by the principle of mechanical lever.The newly developed direct shear apparatus were mainly composed of platform,loading system,distortion measuring system,real-time image displaying system and so on.It is not only simple in structure and convenient in operation,but also low in cost and high precision.The small load direct shear apparatus was compared and analyzed in the principle of instrument,test period and result of direct shear test.In order to verify the reliability of the direct shear apparatus,the results of direct shear test were compared with the result of PFC.The main results of study are as follows:The small load direct shear apparatus has higher accuracy for small load rock joint.The principle of mechanical lever was applied to the direct shear apparatus to keep normal stress constant,which can ensure the reliability and stability of rock joint shear strength.Compared with the conventional direct shear apparatus,the small load direct shear apparatus can shorten the test period of about 85%.

Discussion on the Effect of Sampling Mode on the Properties of Collapsible Soil

Wang Weili, Gao Guangliang, Zhao Pei

2018, 32(6): 277-281,320. doi: 10.3969/j.issn.1007-2993.2018.06.002

[Abstract](56) [PDF 1126KB](7)

Abstract:
In order to analyze the effect of sampling mode on collapsible soil with strong structure,two collapsibility tests were carried out in the site,and the collapsibility characteristics of shallow fine grained soil in the site were basically identified.The laboratory test was carried out on the soil samples of three different sources of impact drilling rig,artificial digging and rotary drilling rig.The test results show that the impact drill sampling of collapsibility coefficient decreased obviously,analyze the reasons for the impact of sampling has great influence on the collapsible soil density and compression modulus;while rotary drilling sampling has a significant impact on the collapsible soil water content.Because of filling of soil pore by water,directly led to the increase of soil saturation and density.Through the analysis of the relationship between the collapsibility coefficient and the density,the size of collapsibility coefficient is anti-correlation with the size of density,and the density was about 1.90~1.95 g/cm³,the soil in the field no longer has collapsibility.The data have some reference significance for the research and production of collapsibility-treatment.

The Evaluation Approach Study on the Hazard of Shallow Embedded Goaf Collapse

Peng Youbao, Zhang Yuxiang, Kang Kai

2018, 32(6): 282-287,316. doi: 10.3969/j.issn.1007-2993.2018.06.003

[Abstract](53) [PDF 9203KB](13)

Abstract:
In view of the complexity and uncertainty of shallow embedded goaf,the effective method for evaluating the hazard of goaf collapseis lacked at present.Based upon detailed investigation and probing for shallow embedded goaf,the quantitative fuzzy comprehensive approach on the basis of analytic hierarchy process for evaluating goaf collapse is put forward.First,on the basis of analysis of geological conditions and the goaf collapse mechanism as well as the influential factors in the research area,the evaluating factor system and criteria for goaf collapse are to be established.Second,in accordance of the difference between discrete variable and continuous variable,the expert judging method and appropriate membership idea function model are employed respectively in constructing membership idea matrix.Simultaneously,the weight numbers can be obtained by applying eigenvector method of analytic hierarchy process.Last,the evaluation vector quantity can be attained through weigh number matrix and membership idea matrix compositional operations.The hazard grade level will be determined by applying the fuzzy nearness degree principle.This paper shows that the comprehensive fuzzy evaluation approach is practical and effective in the aspect of evaluating the hazard for shallow embedded goaf collapse.

Key Technologies for Straight Wall Closely Crossing Underneath the Existing Tunnel

Zhang Qinxi, Sun Yang, Li Songmei

2018, 32(6): 288-293,312. doi: 10.3969/j.issn.1007-2993.2018.06.004

[Abstract](56) [PDF 25148KB](10)

Abstract:
Undercutting interval of Jishuitan station-North Taipingzhuang station in the line of the Beijing subway closely crosses underneath the existing tunnel of the Line 2,Due to restrictions on construction conditions,use the method of straight wall.Through the introduction of straight wall structure design,the reason,design method,calculation process,construction process,numerical simulation and key technologies in the design and construction of straight wall are described in detail.Crack width is 0.19 mm,reinforcement rate is 0.6%which shows that the calculation parameters in the design are more reasonable.Numerical simulation analysis shows that cumulative maximum settlement of existing structures is 2.45 mm,the maximum lateral displacement is 0.15 mm which indicate the rationality of the design and construction process.

Community Geospatial Information Management System Based on EasyEarth

Li Jie, Guo Miwen, Jia Gao

2018, 32(6): 294-297,302. doi: 10.3969/j.issn.1007-2993.2018.06.005

[Abstract](62) [PDF 28513KB](7)

Abstract:
This paper combines GIStechnology with BIM refined model technology,by deeply researching surveying engineering and community management business,and uses information technology and intelligent mode to build community geospatial system based on EasyEarth platform and relational database.The system uses GIS technology's powerful data storage and analysis capabilities to manage community information in a unified manner,and obtain real-time dynamic data through multi-source sensor technology to realize three-dimensional visual management of community geospatial information.Through the system,it can directly manage multi-source and multi-type community data,greatly reduce the complexity of community geospatial information management,save human and material resources,and design real-time monitoring and early warning module to alert community emergencies and provide real-time data analysis.Used to assist decision making.Through the exploration and research of GISsystem in community geospatial information management,I hope to provide reference for GIS technology in refined and real-time community data management.

A Review of Recent Deposited Loess

Wang Yunnan, Tang Guoyi, Zheng Jianguo

2018, 32(6): 298-302. doi: 10.3969/j.issn.1007-2993.2018.06.006

[Abstract](61) [PDF 1113KB](16)

Abstract:
The newly accumulated loess is distributed in the shallow surface,and is mostly existing in the holding layer,but the engineering property is different from the general collapsible loess.In order to avoid engineering accidents,we can take effective measures to deal with the newly accumulated loess in actual engineering.In this paper,we summarize the progress of the recently accumulated loess in the three aspects of discriminant method,engineering characteristic and foundation treatment,and analyzes the advantages and disadvantages of them,finally put forward the outlook for the next phase of the study.

A Brief Analysis of the Transient Surface Wave Test in Engineering Investigation

Yang Lina, Dai Yanxiong

2018, 32(6): 303-305. doi: 10.3969/j.issn.1007-2993.2018.06.007

[Abstract](57) [PDF 4789KB](12)

Abstract:
Transient surface wave test is a type of geotechnical engineering field test.It use the dispersion and speed information which produced by the surface wave in one wavelength range spreading in different soil and rock medium.Through the test software,to synthesize as a surface wave section profile color image that reflect the characteristics of stratum elastic structure,in order to interpret the difference in wave velocity.This article takes an Seychelles project as an example to discuss the engineering practice that in the case of being lack of exploration work space,difficult to identify the strata just with simple exploration ways,using the transient surface wave test comparing with engineering exploration data.Meanwhile,the article briefly analyzes the advantages and limitations according to the situation that we using the transient surface wave test on site.

Study on the Design Method of Grouting Steel Inclined Support in the Foundation of Clay Area

Zhao Tianchi, Fei Wei, Zhu Huogen

2018, 32(6): 306-312. doi: 10.3969/j.issn.1007-2993.2018.06.008

[Abstract](57) [PDF 4956KB](17)

Abstract:
Sheet piles&reinforced concrete supports are generally applied as the supporting structure of basements' foundations in the clay area.Too much inner supports,however,has a negative impact on the construction and slow down the velocity of excavation.This paper applies a supporting structure to clay area which is made up of sheet piles and grouting steel inclined supports and commonly used in hard soil.The exchange and dismantlement of supports are not needed in this structure,so the construction time can be saved.A method of calculating the bearing capacity and equivalent stiffness in design has been presented in this paper.Finally an example is used to validate the design theory and show the availability of the grouting steel inclined support.

The Research of Large Deformation Mechanism and Control Countermeasures of Excavations under Deep Soft Soil Area

Geng Yekuan, Gao Fenfen, Zhou Chengjun

2018, 32(6): 313-316. doi: 10.3969/j.issn.1007-2993.2018.06.009

[Abstract](46) [PDF 2446KB](10)

Abstract:
Considering the "time and space effect" of deep excavations in soft soil area is significant,based on excavations case in Hexi area,Nanjing,the mechanism of large deformation of excavations under deep soft soil is analyzed.Comprehensive control measures such as supporting reinforcement,load limiting,unloading,isolation piles,reinforcement and thickening cushion,and floor construction are adopted,the deformation rate of excavations is effective controlled,which guarantees the evcavations to be carried out safely and smoothly.It provides reference for deformation control of excavations engineering in similar soft soil area.

Combined Application of SMW Method in Deep Foundation Pit Support in Soft Soil Area

Hu Jing, Sun Yansheng, Zhang Jingjing

2018, 32(6): 317-320. doi: 10.3969/j.issn.1007-2993.2018.06.010

[Abstract](64) [PDF 2078KB](15)

Abstract:
A deep excavation located at the soft soil area of Tianjin is taken as an example,which supporting pile with cast-in-place pile and SMW method.According to the monitoring results and on-site construction feedback,the combination support type can meet the requirements of foundation pit safety,effectively reduces the cost,significantly shortens the construction period and provides reference for the design and construction of similar foundation pit engineering.

Analysis on the Impact of the Range of Cement-Soil Reinforcement in Passive Area of Foundation Pit on the Displacement Support in Soft Soil Area

Li Lingfeng, Wei Haitao

2018, 32(6): 321-323. doi: 10.3969/j.issn.1007-2993.2018.06.011

[Abstract](63) [PDF 2264KB](11)

Abstract:
This paper analyzes the impact of reinforced depth and reinforced width on the displacement of the foundation pit when the soil in the passive zone of the foundation pit is reinforced with cement.Based on an example of a foundation pit project in Shanghai,the rational depth and width of cement-soil in the passive zone of a similar project are summarized.

2018 Vol. 32, No. 6